Angioplasty, also referred to as percutaneous transluminal angioplasty (PTA) or percutaneous transluminal coronary angioplasty (PTCA), is a method for the widening or reopening of constricted or closed blood vessels (typically arteries, more rarely also veins). A common method of angioplasty is balloon dilation.
Balloon dilation in the context of angioplasty is understood in interventional radiology, cardiology, and vascular medicine as a method for expanding pathologically constricted blood vessels using a balloon catheter, a vascular catheter having balloon attached thereto, which only unfolds slowly under high pressure (often 6-20 bar) at the constricted location. The narrow points, which arise, inter alia, due to atherosclerotic changes (vascular calcification), are thus stretched so that they no longer obstruct the blood flow or obstruct it less.
The balloon catheter is almost always placed from the groin via a guide wire and guide catheter in the stenosis (narrow point) and inflated using pressure. The narrow point is typically remedied in this way and an operation is avoided.
Modern methods in the field of plastic processing allow the design and refinement of such balloons to adapt the quality individually to the requirements of the patients. The flexibility of the balloons and their pressure resistance are important for this purpose.
The drug-releasing balloon catheter (also known as a drug-eluting balloon or drug-coated balloon) is a refinement of the typical balloon catheter.
The balloon surface is at least partially coated with a drug or medication, which is applied at the point of the vascular constriction by the dilation of the balloon, in order to pharmacologically support and stabilize the vascular expansion. In contrast to stent therapy, a mechanically acting foreign body does not remain in the body after the intervention.
A cytostatic agent, for example, paclitaxel because of its rapid penetration into the vascular wall, can be used as the drug for this purpose. In addition, an additive is frequently added to the medication, which encourages the absorption of the medication in the vascular wall.
Various methods are known for applying drugs or medications to a balloon catheter:
1) embedding the drug in a microporous surface of the balloon;
2) coating the balloon with drug-containing polymer layers (base coating, drug depot).
In the typical method, the majority of the drug is applied below the folds of the non-dilated balloon. An uneven distribution of the drug over the dilated balloon surface and later also over the surface of the dilated vessel thus results.
The drug is frequently applied to the balloon by immersion or spraying. The externally remaining component of the drug can flake off in an uncontrolled manner upon the later dilation, so that the release of the introduced drug also cannot be exactly controlled.
During the insertion and positioning of the catheter at the action location, the catheter is also subject to greatly varying mechanical strains, which may result in the loss of the coating. These include, for example, the removal of the protector, touching of the balloon by the operator, buckling of the balloon, the insertion of the catheter into the so-called “introducer”, the friction in the guide catheter, friction on the vascular wall or other materials such as blood in the vessel, and, in particular with calcified lesions, a high level of mechanical influence.
The loss of pharmacologically active substance already on the way to the target location makes it necessary to charge the balloon catheter with a significantly higher quantity of drug than would actually be necessary for the desired effect.